GBL is industrially produced through hydrogenation reaction of maleic anhydride or succinic anhydride resulting from partial hydrogenation of maleic anhydride, dehydrogenation reaction of 1,4-butanediol, or the like. For example, a method of obtaining GBL through hydrogenation of a succinic acid derivative, such as succinic anhydride, etc., in the presence of a ruthenium-based catalyst; and a method of obtaining GBL through dehydrogenation reaction of 1,4-butanediol are known (Patent Document 1 and Patent Document 4).
However, according to the conventional production method of GBL, it was difficult to remove acid components, for example, organic acids, such as succinic acid, maleic acid, butyric acid, gamma-hydroxybutyric acid, propionic acid, etc., in GBL, and the like, and therefore, there was a limit in application to uses in which GBL is required to be high in purity and neutral as a solvent.
For the purpose of removing such acid components, there is a proposed a method in which an oxide or hydroxide of an alkaline earth metal is added to GBL and thermally treated, followed by distillation (Patent Document 2). In addition, for the same purpose, there is also disclosed a method in which a carbonate of an alkali metal or alkaline earth metal is brought into contact with a crude 5-alkyl-γ-butyrolactone, thereby removing by-produced acid components (Patent Document 3).